How to Run a ZIO ActorSystem?

[christophknabe]

In https://github.com/zio/zio-actors/blob/master/docs/usecases/pingpong.md is a Ping Pong example with ZIO Actors. However when I am trying to run it using "dev.zio" %% "zio-actors" % "0.0.9" I do not see any Ping! or Pong!.
I suppose it is something basic. Would be nice if you could give me a hint or complete your Ping Pong example. My code trying to run it (simplified by removing the remote parts) is shown here. The output is only ZIO App completed successfully with result ().

package zio_actors

import zio.ExitCode.{failure, success}
import zio.actors.Actor.Stateful
import zio.actors._
import zio.{RIO, Runtime}
import zio.console._

//Taken from https://github.com/zio/zio-actors/blob/master/docs/usecases/pingpong.md
//but without Remoting
object PingPongMain {

  sealed trait PingPong[+_]
  case class Ping(sender: ActorRef[PingPong]) extends PingPong[Unit]
  case object Pong extends PingPong[Unit]
  case class GameInit(recipient: ActorRef[PingPong]) extends PingPong[Unit]

  val protoHandler = new Stateful[Console, Unit, PingPong] {

    override def receive[A](
        state: Unit,
        msg: PingPong[A],
        context: Context
    ): RIO[Console, (Unit, A)] = {
      msg match {
        case Ping(sender) =>
          for {
            _ <- putStrLn("Ping!")
            _ <- sender ! Pong
          } yield ((), ())

        case Pong =>
          for {
            _ <- putStrLn("Pong!")
          } yield ((), ())

        case GameInit(to) =>
          for {
            self <- context.self[PingPong]
            _ <- to ! Ping(self)
          } yield ((), ())
      }
    }

  }

  val program = for {
    actorSystem <- ActorSystem("PingPongActorSystem")
    firstPlayer <- actorSystem.make("firstPlayer", Supervisor.none, (), protoHandler)
    secondPlayer <- actorSystem.make("secondPlayer", Supervisor.none, (), protoHandler)

    _ <- firstPlayer ! GameInit(secondPlayer)
  } yield ()

  //The main method is written by me.
  def main(args: Array[String]): Unit = {
    val exitCode = Runtime.default.unsafeRunSync(program)
    // All errors are mapped to exitCode 1, all successes to exitCode 0.
      .fold(cause => failure, result => { println(s"ZIO App completed successfully with result $result"); success })
    System.exit(exitCode.code)
  }

}

[christophknabe]

In the meantime I found the reason for not ping-ponging. The main method exits too early. Thread.sleep(2000) did not help, even in another thread. But using the ZIO means for retaining the execution live helped. I had to use delay and zipPar. The following main method gives the program enough time to execute:

def main(args: Array[String]): Unit = {
  val minSeconds = 2
  import zio.duration._
  val delayed = UIO.unit.delay(minSeconds.seconds).map(_ => s"$minSeconds seconds passed")
  val exitCode = Runtime.default.unsafeRunSync(program.zipPar(delayed))
    .fold(_ => failure, result => { println(s"ZIO App completed successfully with result $result"); success })
  System.exit(exitCode.code)
}

The output now texts:

Ping!
Pong!
ZIO App completed successfully with result ((),2 seconds passed)